deprecate support for Ubuntu 14.04

Author: Kautenja

.travis.yml

@@ -2,14 +2,14 @@
 language: python # this works for Linux but is an error on macOS or Windows
 matrix:
   include:
-    - name: "Python 3.5 on Ubuntu 14.04"
-      python: 3.5
-      dist: trusty
-      before_install: pip3 install scons
-    - name: "Python 3.6 on Ubuntu 14.04"
-      python: 3.6
-      dist: trusty
-      before_install: pip3 install scons
+    # - name: "Python 3.5 on Ubuntu 14.04"
+    #   python: 3.5
+    #   dist: trusty
+    #   before_install: pip3 install scons
+    # - name: "Python 3.6 on Ubuntu 14.04"
+    #   python: 3.6
+    #   dist: trusty
+    #   before_install: pip3 install scons
     - name: "Python 3.5 on Ubuntu 16.04"
       python: 3.5
       dist: xenial